The role of plant chemical cues in determining host preference in the generalist aphid parasitoid Aphidius colemani

The host preference behaviour of the generalist aphid parasitoid Aphidius c olemani was investigated using a Y-tube olfactometer. Female A. colemani sh owed a preference for the host-plant complex on which they had been reared, even though the same aphid host was involved, demonstrating a host plant p reference. This preference was not evident when the parasitoids were dissec ted from their mummies prior to adult emergence. Host plant preference exhi bited during host selection appeared to be induced by chemical cues encount ered on the mummy case at the time of emergence, but preferences could be c hanged by subsequent foraging experiences. It is concluded that plant chemi cal cues play a major role in determining initial preferences through a pro cess of emergence conditioning but that learning processes, involving cues encountered during oviposition in or contact with the host, can modify thes e initial preferences.